Biology ETDs

Publication Date

3-23-1977

Abstract

A technique using simultaneous bilateral radiographic exposures of the bronchial tree of Syrian hamsters was used to examine clearance patterns of tantalum powder, an inert radiopaque substance. The tantalum powder, nominally 2.5 µm diameter particle size, was insufflated in small amounts ranging from 6 mg to 344 mg into the lungs of 10 animals. In most cases the major bronchi of the lungs were well outlined with tantalum initially, as were several medium and small bronchi. The clearance of the tantalum was noted by making simultaneous radiographic exposures from two directions at exponentially increasing time intervals. Exposures were begun within 3 min. after insufflation and ended after 48 hr. or when no remaining tantalum could be detected in the lungs. Animals were anesthetized for bronchography using halothane, a short-duration inhalation anesthetic. A qualitative description is given of the appearance of various structures of interest in the bronchial tree at successive time intervals as the lungs were cleared of the insufflated tantalum. Some observations include the existence of a highly efficient clearance region in the upper region of the trachea below the larynx and in the main bronchi. Medium and small bronchi varied in clearance rates. Several retention mechanisms were observed in the tracheobronchial tree which resulted in delayed clearance. These were characterized by regions where accumulations were present for prolonged times. An important consideration in the efficiency of clearance is the orientation of specific bronchi with respect to gravity. Bronchi which taper downward tend to fill with tantalum because the density of tantalum is high and accumulations can overwhelm the clearance action of the tracheobronchial escalator in some of these airways. Retrograde clearance motion was observed in certain airways due to the above mechanism. The motion usually resulted in accumulations of tantalum and mucus in distal bronchioles and alveoli. Another phenomenon observed was the aggregation or packaging of medium dense regions into small, more dense clumps prior to removal. This phenomenon may be due to the organization of ciliated cells and mucus-secreting cells in the various bronchi. An overloading effect on a specific area of ciliated epithelium may account for these tantalum accumulations, and mechanical breakup of these regions may be required for clearance to continue. Streaming patterns have also been observed which indicate that there may be preferentially efficient pathways along which most particles travel. Whether particles actually spiral along certain pathways or whether the patterns observed merely appear to be spirals was not resolved. Cartilage rings in the larger bronchi and trachea also were observed to accumulate and retain tantalum. Retention may be due to a slowing of clearance in these areas due to a reduced number of cilia on the cartilage rings or the rings may produce a blocking effect due to their protrusion from the bronchial or tracheal wall into the air space. Following each series of bronchograms, the animals were sacrificed and lung casts made of silicone rubber were obtained. The casts were used to observe details of airway geometry and showed no unusual structural features in any of the animals studied.

Project Sponsors

National Institute of Environmental Health Sciences ERDA Contract EY-76-C-04-1013 under an interagency agreement between National Institute of Environmental Health Sciences (NIEHS) and the Division of Biomedical and Environmental Research of the U.S. Energy Research and Development Administration

Language

English

Document Type

Thesis

Degree Name

Biology

Level of Degree

Masters

Department Name

UNM Biology Department

First Committee Member (Chair)

Marvin LeRoy Riedesel

Second Committee Member

Roger Orville McClellan

Third Committee Member

Paul Richard Kerkof

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